The invention relates to an injection device for administering a liquid product, particularly a medicine, such as insulin for diabetes therapy. In particular, the invention relates to a driving and dosing device for such an injection device.
An injection device having a dose indicating drum and a drive spring is known from the prior art, namely WO 2008/031237 A1. The drive spring is a coiled spring, which is wound in a spiral shape from a strip-shaped material. When the product dose is being set, the spring is tensioned with a rotational movement. In order to inject a dose, a piston rod is coupled to the spring by means of an actuating button at the proximal end of the device, whereby the spring can output the energy stored therein to the piston rod, whereby the piston rod is moved in the discharge direction. To set a new dose, the spring is again cocked by rotating the dosing knob, and so on. This is repeated until the product container has been emptied.
An injection device with a helical spring is also known from U.S. Pat. No. 5,104,380 A, the spring being likewise cocked rotationally during dosing, so that the helical spring can also be referred to as a torsion spring. The spring, cocked by rotation before each product discharge, transfers its energy to the piston rod in order to propel the piston rod.
WO 2006/77466 A2 discloses an injection device that has a direct mechanical drive between the person applying the injection force and the piston rod, which is displaced in the distal direction for the injection of the medicine.